Method of making locking nuts

ABSTRACT

Improved process for applying locking patches of resilient resin to internally threaded articles such as nuts having openings at both ends of the threaded portions in which process there is used apparatus including, a support and treating member, preferably a rotatable, circular table with edge notches complementary to a portion of the exterior of a threaded article to be treated, which receives a succession of threaded articles heated to a temperature above the melting point of the resin to be applied and moves the articles along a path for treatment with the axes of the threaded articles in an up and down position and with the openings at the upper and lower ends of the threaded portions substantially uncovered, conduits on the support and treating member are associated with each threaded article to direct particles of heat fusible resin upwardly through the opening at the lower end of the article against a portion of the threaded surface of the article to form a first deposit of resin on an area of the threaded surface during movement along a first portion of the treatment path and a turning device at an intermediate location on the treatment path turns each threaded article, as it reaches that location, a predetermined angle so that the conduit associated with the article directs resin against a further area of the threaded surface to form a second deposit of resin during movement along a further portion of the treatment path.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of application Ser. No. 572,199 in thenames of Richard J. Duffy, Richard M. Elliott and Philip J. Rodden filedApr. 28, 1975, now U.S. Pat. No. 3,995,074 dated Nov. 30, 1976 which isa division of Ser. No. 396,094 filed Sept. 10, 1973 and now U.S. Pat.No. 3,894,509 issued July 15, 1975.

The present invention relates to an improved process for the manufactureof self-locking internally threaded elements and more particularly forthe continuous manufacture of elements such as fasteners wherein theself-locking feature is obtained through a deformable plastic patchsecured onto the threaded internal surface of the element.

In U.S. Pat. No. 3,858,262 entitled "Method of Making Self-LockingInternally Threaded Articles" filed in the name of R. J. Duffy, andassigned to the assignee of the present invention, there is disclosed amethod and apparatus for making a self-locking threaded element whichavoids the difficulties of resin deposit on the end faces of thethreaded element and, is effective to deposit resin on the threadedsurface in the selected area with a minimum of spatter on other portionsof the threaded surface. In that method and apparatus as disclosed, anut or other internally threaded member was heated, and while mountedwith its axis in an up-and-down position the threaded surface wassprayed with finely divided resin particles which were caught and builtup on the heated surface to form a plastic body.

In U.S. Pat. No. 3,894,509 there is disclosed an apparatus and methodfor mass production of such internally threaded elements including anautomatic means to move a succession of internally threaded elementthrough various stations in which the elements are loaded onto aconveying and treating member, a resilient resin locking patch is formedon the threaded surface of the elements by deposition of heat fusibleresin powder and the elements are unloaded at a substantial rate.

While the apparatus and method disclosed in these patents and thelocking action of the applied patch have proven quite satisfactory formost uses, it has been desired to provide greater locking torque forcertain uses. Increase in the amount of resin applied to form a thickerlocking patch gives some increase in locking torque but the increaseobtainable is limited since an excessively thick patch causes difficultyin assembly and the generation of chips due to shearing off of portionsof the patch.

It is an object of the present invention to provide an improved methodfor the manufacture of self-locking internally threaded elements whereinlocking bodies of resilient resin giving improved locking torque areformed by application of fine particles of heat fusible resin.

SUMMARY OF THE INVENTION

To these ends and in accordance with the present invention, there isprovided a process for applying resilient resin to internally threadedarticles such as nuts having openings at both ends of the threadedportions in which the articles in heated condition are conveyed on asupport in a path for treatment and conduits direct heat fusibleparticles to a first area of the threaded surface of each article onwhich a patch is to be formed, and a device turns the articles abouttheir axes at an intermediate point along said path so that the conduitsdirect resin against second areas of said threaded portions duringmovement through the remainder of the path.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the invention, reference should bemade to the following description of a preferred embodiment, taken inconjunction with the drawing thereof, wherein:

FIG. 1 is a perspective view showing a device for the manufacture ofself-locking threaded fasteners constructed in accordance with theteachings of the present invention;

FIG. 2 is a top plan view of the device shown in FIG. 1 having portionsof the structure broken away to reveal underlying features;

FIG. 3 is a sectional elevational view taken along the line III--III ofFIG. 2 showing details of the construction;

FIG. 4 is a sectional elevational view taken along the line IV--IV ofFIG. 2 showing further details of the structure;

FIG. 5 is a sectional plan view taken along the lines V--V of FIG. 4showing that portion of the structure in detail;

FIG. 6 is a plan view showing a portion of the structure depicted inFIG. 2, taken on an enlarged scale for clarity;

FIG. 7 is an elevational view of the structure shown in FIG. 6;

FIG. 8 is a plan view showing another portion of the structure depictedin FIG. 2, taken on an enlarged scale for clarity;

FIG. 9 is an elevational view of its structure shown in FIG. 8;

FIG. 10 is a perspective view of the device shown in FIG. 1 havingportions of the structure broken away to show underlying features; and

FIG. 11 is a fragmentary plan view on an enlarged scale of the structureshown in FIG. 10 illustrating the nut turning action.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following discussion, the process will be described primarily asit relates to the treatment of nuts but it is to be understood that theprocess will be useful for treatment of internally threaded articlesopen at both ends other than nuts.

According to the present invention we have discovered that in operationof the treating apparatus and method of the parent patents usingcomparable temperatures, resin supply rates, article supply rates andother conditions, major improvement in locking torque is secured bydepositing a portion of the heat fusible resin particles on one area ofthe hot threaded surfaces and thereafter depositing the remainder of theresin particles on a further area of the threaded surfaces. Operating inthis fashion, not only is the locking torque increased but difficultiesdue to unwanted deposition of resin on face portions of the nuts and onlead threads for starting the nuts are avoided.

Also in the high speed treating apparatus of the parent patents, whilethe succession of nuts oriented in flat-to-flat relation resembles achain which meshes with the notches of a threading table supportvisualized as a sprocket, the leading and trailing flats of each nut onthe table support are in fact substantially radially disposed. Flats ofadjacent nuts on the table support diverge and provide some clearancebetween outer portions of these radial flats and this clearance pluslimited "give" of the adjacent nuts in their notches enables the nuts tobe turned one flat by a simple turning device, such as a resilientpresser member acting on the outer portion of the nuts counter to themovement of the table support, and to be restored to their notches intheir turned position without removal of the nuts from the support.Since the resin applying conduits of the apparatus of the parent patentsare in fixed relation to the notches on the rotating table support, thecombination of the turning device, disposed at an intermediate locationof the path in which resin is applied to the nuts, with the notchedtable support and the fixed conduits enables deposition of a portion ofthe resin particles on first areas of the threaded surfaces until theturning device is reached and deposition of the remainder of the resinparticles on further areas of the threaded surfaces during movement ofthe nuts through the remainder of the resin applying path.

Referring to the drawing, and in particular to FIGS. 1 and 2, there isshown apparatus for the manufacture of a self-locking internallythreaded article in the form of a hex nut N which generally comprises arotatably mounted transport member in the form of a table 10 movablealong a predetermined rotary path about its central axis, in thedirection shown by the arrows of FIGS. 1 and 2.

As the table 10 is continuously rotated about a fixed housing 11, apoint on the table 10 will be seen to pass through a plurality ofstationary work areas which will be termed stages of the operation forthe purposes of the present description.

During the first stage of operation, a loading chute 12 which isinclined downwardly toward the surface of the table 10 is effective todeposit the hex nut N onto the table, and during a next stage, aresilient thermoplastic material in powdered form is applied in twoportions to angularly spaced areas of the internally threaded surface ofthe nut. This stage is substantially enclosed by a vacuum hood 13, theoperation of which will be explained in detail hereinbelow.

During a next subsequent stage, a second upwardly inclined chute 14having one end disposed adjacent the table 10 is effective to unload thenut N from the table 10, which is followed by the subsequent stage ofoperation which substantially covers that portion of the table 10located between the unloading station and the loading station, andwherein the means for applying thermoplastic material to the nut N arepurged of residual material, and are readied for the next sequence ofoperation.

It will be noted in FIG. 1, that the stationary housing 11 is providedwith a funnel shaped hopper 15 which serves to receive the powderedresilient thermoplastic resin for application to the internal threads ofthe nuts N, which operation will be explained in detail below.

Referring now to FIGS. 2-5, and in particular to the table 10, the tableis shown to comprise a hub 16 having a plate 17 affixed to its uppermostsurface and a groove 18 for receiving a V-belt 19 which is connected toa motor (not shown). The hub 16 is slidingly engaged on the centralhousing 11 and is caused to rotate by the motor driven belt 19, the hubbeing supported by a pair of bearings 20 and 21.

Referring still to these FIGS. 2-5, the hub 16 is shown to have formedtherein a plurality of circular cross section apertures 22 each havingan opening internally toward the housing 11 and receiving at theopposite end a tube 23, the tube and aperture forming in combination aconduit means, as will be explained further in detail.

As best shown in FIG. 2, the outer periphery of the plate 17 is providedwith a plurality of V-shaped slots or notches 24, each of which has atongue 25 disposed below and extending outwardly from the respectiveslot or notch to form a pocket or cavity for receiving a threaded hexnut N, of the type shown. Each of the tubes 23 has a channel bracket 26connected to it by welding or other means and a plurality of fasteners27 serve to connect the bracket 26 to the plate 17, with the respectivetongue 25 sandwiched therebetween. Each of the tongues 25 has a circularopening provided therein and the outer end of the tube 23 is bentupwardly at approximately a 45° angle to extend through the circularopening in the tongue, and slightly above the tongue to a position whichwould locate the outer end of the tube within a hex nut received in thepocket formed by the respective V-shaped slot or notch 24.

Referring in particular to FIGS. 3, 4 and 5, the housing 11 is seen tohave formed therein a hollow central opening 28 into which the hopper 15is introduced, and which extends to a point near the bottom of thehousing. The bore 28 is flanged outwardly near its midpoint, and has aslotted opening 29 which extends for substantially 180° around thehousing 11 except for a blocked section 29(a) intermediate the length ofthe slotted opening 29. The slot leads from the flanged out portion ofthe bore 28 externally of the housing 11 and is in alignment with theplurality of apertures 22, when the table 10 is located on the housing11. A conical shaped divider 30 is located in the flanged out portion ofthe bore 28 and is attached to the wall of the bore at that portion ofthe wall which is not cut away by the slotted opening 29. Thus, thedivider 30 separates the upper portion of the bore 28 from the lowerportion over the entire circumference of the bore with the exception ofthat portion where the slotted opening 29 is located.

An inlet opening 31 extends into the bore 28 at its lowermost extremityand is connected to a source of fluid pressure such as an air pump (notshown).

Diametrically opposite the slotted opening 29 and near the outer edge ofthe housing 11 are located a plurality of vertical circular cavities 32,four in number, which re best shown in FIG. 2.

Each cavity 32 has its lower end terminating in a larger diameterchamber 33, and its upper end terminating at a second slotted opening 34similar to the diametrically opposed slotted opening 29. In thisinstance, the slotted opening 34 extends from the outer periphery of thehub 11 over a circumference of about 150° to an inner wall 35 as shownin FIG. 2. The slotted opening 34 is in alignment with the apertures 22and therefore forms a flow path from the tubes 23 through the chamber 33to which a vacuum source (not shown) is connected, when the tubes 23 aremoved into the area over which the opening 34 is formed.

Referring in particular to FIGS. 3 and 4, it will be noted from theconstruction that the table 10 is readily removable from the hub 11 byvirtue of the removable retaining plate 36 which is secured by fourfasteners in the form of screws 37. When the screws 37 are removed, theretaining plate 36 may be lifted from the structure and the table 10removed and subsequently replaced with a table serving to receiveinternally threaded fasteners of a different size or shape than thosewhich are accommodated by the table 10 shown.

Because of the necessity to provide a sliding fit between the table 10and the central housing 11, there is a distinct possibility of materialwhich is being transferred between the tubes 23 and the slotted opening29, or the tubes and the slotted opening 34, tending to escape betweenthe outer surface of the hub 11 and the inner surface of the hub 16 ofthe table 10. There is provided, therefore, a pair of circumferentialgrooves 38 and 39 formed in the hub 11 and extending completely aroundthe hub. At a point adjacent the inner wall 35 of the slot 34 a verticalbore 40 extends upwardly through the housing 11 and is provided with apair of passages 41 and 42 which terminate at the grooves 38 and 39. Aduct 43 extends from the bore 40 and is connected to a source of airpressure (not shown) for providing a fluid pressure in the bore 40.Thus, material having a tendency to find its way between the hub 16 andthe housing 11 is inhibited from doing so, as any air flow occurringtakes place from the grooves 38 and 39 into the openings 29 and 34.

Referring now to FIGS. 1 and 2, it will be observed that the vacuum hood13 is divided into two portions for purposes of convenience only, andboth portions taken together cover the area about the housing 11 whereinthe slotted opening 29 is formed. That is, the entire area over whichthe thermoplastic resin in powdered form is fed through the tube 23 iscovered circumferentially by the hood 13. Both of the portions of thehood 13 are constructed substantially the same and therefore only thefirst portion as shown in FIG. 1 will be described in detail.

Each of the hood portions is provided with a chamber 44 which issupplied with a negative pressure by vacuum producing means (not shown).A cover plate 45 extends outwardly from the hood 13 to a position overthe table 10 which serves to cover a nut N located on the table. For thepurpose of equalizing the vacuum throughout the hood 13, a plurality ofpartitions 46 are located within each of the portions of the hood 13 andserve to form a plurality of separate vacuum areas, each havingsubstantially the same negative pressure to apply to the area above thenut N located adjacent to the opening of the hood.

The feeding arrangement shown comprises the chute 12 which is supportedadjacent the periphery of the table 10 and positioned with the lowermostdischarge surface of the chute spaced slightly from the surface of theplate 17 and having an outer rail 47 extending beyond an inner rail 48as best shown in FIGS. 6 and 7. The distance between the outer rail 47and the inner rail 48 is substantially the width across the points ofthe hex portion of the nut N to be fed onto the table 10. Thus, as shownin FIGS. 6 and 7, the nuts orient themselves flat-to-flat when travelingdown the chute 12 and are therefore aligned for engagement with theV-shaped slot 24 on the table 10. A segment 49 of the chute 12 ismanufactured of a material with suitable non-inductive andheat-resistant properties, and extends through an induction coil 50which is suitably sloped and located adjacent the chute segment forheating a nut N traveling through the segment. The nut N may be fed byany suitable commercial feeder, of the vibrating type or of any othertype, and as such devices are well known in the art, they are notconsidered to be of importance in describing the present invention andtherefore the feeder has not been shown.

As can be seen from FIG. 2, with the nuts oriented flat-to-flat, thesuccession of nuts may be visualized as a chain of which the points meshwith the 120° slots 24 of the plate 27 which may be visualized as asprocket.

However, with respect to any given nut in the succession of nuts on thetable 10, it will be seen that the flats of adjacent nuts define, withthe walls of the notch related to the given nut, a deep slot of whichthe side walls defined by the flats of the adjacent nuts diverge due tothe radial orientation of the nuts. The clearance between the flats ofthe given nut and the diverging walls of the slot provide limitedfreedom of rotation of the given nut which is important for turning ofthe nut as discussed below:

The rotation of the table 10 at uniform speed serves as the speedcontroller for the system. As each nut N approaches the lower end of thechute 12, it is lowered down over the orifice of a tube 23, and alsogradually comes into meshing engagement with the V-shaped slot 24 of theplate 17. As the table 10 then rotates, the nut moves further forward.The nut is found to be guided into close engagement with the 120° slotby the outer rail 47 of the chute 12, even at speeds of approximately600 fasteners per minute.

At the opposite side of the table 10 from the chute 12 there is locateda similarly constructed chute 14, as best shown in FIGS. 8 and 9 takenin conjunction with FIG. 1. The chute 14 is effective to remove the nutsN from the table 10 and in a similar manner to chute 12 is sloped withits lowermost end, which in this instance is the nut receiving end,disposed adjacent the top of the table 10 and has an outer rail 51 whichextends beyond an inner rail 52, both rails being spaced substantiallythe distance across the hex portion of a nut N. The uppermost end of thechute 14 may be left open providing for the nuts N to be dropped into areceptacle (not shown) or may lead to another chute or conveyance forcarrying the nuts to a subsequent work or storage area.

With respect to the particular construction of the chutes 12 and 14, theouter rail 47 of the chute 12, as viewed in FIG. 6, forms a means forguiding the nut N into the proper location in the V-shaped slot 24 ofthe table 10 after which the nut may be held in place by resilientpressure means such as spring clips 60 to provide a radial retainingforce to the nuts.

At an intermediate portion of the path of travel between chute 12 andchute 14 corresponding to the location of the blocked section 29(a) inthe slotted opening 29, there is provided a device for turning thetreating hex nuts, the angle of turn will be 60° or a multiple of 60°corresponding to the radial angle between adjacent corners of the hexnuts. The turning device shown is a resilient finger 62 disposed toengage an outer flat 64 of a hex nut N adjacent the outermost corner 66as the nut N is moved by the table and to create a turning moment whichrotates the nut N out of its initial position as shown in FIGS. 10 and11. The clearance between the nut N being turned and the diverging flatsof adjacent nuts facilitates initial rotational movement so that therelatively small turning moment is sufficient, as shown in FIG. 10 toturn the nut N somewhat more than 1/2 the radial angle 60°, required tobring the corner 68 of the nut N into alignment with the angle of thenotch 24. This initial movement brings the opposed corners 78 and 80 ofthe nut N into engagement with the flats 74 and 76 of the adjacent nutsto spread them apart against the resilient retaining action of thesprings 60. The pressure of the flats 72 and 76 against the corners 78and 80 of the nut N being turned, and the force of the spring 60 againstthe corner 76 of that nut N completes the turning and returns the nut Nto its notch in turned position with a new area of threaded surfaceexposed to particles of heat fusible resin from the tube 23. During theturning action, the blocked section 29(a) allows passage of air butstops flow of resin particles through the tube 23 to avoid deposition ofresin on undesired areas of the nut. It will be understood that a nutmay be given additional turns for greater spacing between resin depositsor for additional resin deposits if desired by providing additionalturning devices and appropriate blocked sections.

When nuts have been carried to the discharge point, the outer rail 51 ofthe chute 14 serves to retain the nut in registry with the slot 24 untilsuch time as the nut is lifted above the table and the inner rail 52serves to combine with the rail 51 to guide the nut along the chute toits destination.

In operation, the apparatus as herein disclosed is first prepared byloading the hopper 15 with a thermoplastic resin in powdered form. Thematerial may be a powder which is a mixture comprising a major portionof powdered polyamide resin, (nylon 11) and a minor proportion of epoxyresin having a particle size distribution such that less than 2% isretained on a No. 70 sieve, about 90% retained on a No. 140 sieve andabout 5% passing a No. 325 sieve. This is substantially the samematerial as disclosed in the prior referenced U.S. patent applicationSer. No. 572,199 filed in the name of Richard J. Duffy and assigned tothe assignee of the present invention.

While the means for introducing thermoplastic resin in powdered form tothe apparatus has been shown as a funnel type hopper 15, it should beunderstood that for the purposes of the invention the material could beprovided from a remote source and continuously supplied by a suitableconduit to the housing 11. It should also be understood that the flow ofresin material is metered by valving or other means well known in theart so as to control flow rate according to the production rate, nutsize, thread size or temperature variations.

With the material introduced into the apparatus, the means for providinga vacuum to the chamber 33 and the duct 43, and the means for providingair pressure to the inlet opening 31 are activated. Also external to thehousing 11, the means for providing a vacuum to the hood 13 isinitiated, and the induction coil 50 is energized to provide heating ofthe nuts N as they are directed along the chute 12.

With the preliminary steps set forth above having been taken, theapparatus is in the ready state and the motor means for driving the belt19 and means for feeding the nuts N onto the chute 12 are activated toinitiate processing of a typical batch of internally threaded fasteners.As the table 10 rotates at about 10 revolutions per minute in thedirection of the arrows shown in FIGS. 1 and 2, the nuts N areintroduced into the chute 12 and travel flat-to-flat through theinduction coil 50 where each nut is raised to a temperature sufficientto cause the above described thermoplastic powder to adhere to thethreaded surface of the nut when contacted thereby, and to be fused byheat from the surface to form a continuous plastic body. As a nut Napproaches the table 10 it is retained on the chute 12 by the outer rail47 until it is in registry with a V-shaped slot 24 and therebypositioned over a respective tube 23 disposed with its discharge openingat the threaded opening of the nut. It is important that the slots ornotches 24 be so spaced that the nuts N are not wedged together so thatthere is a little play between adjacent nuts N in the succession ofnuts. The table 10 is rotated at a constant speed (about 10 revolutionsper minute) and each nut N remains on the table for about 1/2 revolutionor about 3 seconds with the discharge opening of the hollow tube 23disposed to project slightly into the threaded opening of the nut.

As the table 10 rotates, each tube 23 is moved such that its respectiveaperture 22 comes into registry with the slotted opening 29 and the nutlocated adjacent the tube discharge opening is simultaneously disposedbelow the cover plate 45 of the hood 13. Air is supplied through theinlet opening 31 and into the lower portion of the hollow bore 28 whereit passes into the slotted opening 29. The air flows horizontallythrough a converging area to the slotted opening 29 past the powder slotformed by the wall of the bore 28 and the conical shape divider 30 whereit picks up the powder and then passes through a diverging area. Thepowder is fed at a uniform rate to the powder slot and theconverging-diverging areas produced by the air passing from the portionof the bore 28 adjacent the divider 30 and into the slotted opening 29provides a slight suction or "Venturi effect" at the powder slot whichis considered to draw the powder into the air stream. The slottedopening 29 and its powder slot between the divider 30 and the bore 28extend for about 180° about the housing 11, the deposit of powder of thefirst area of threaded surface of the heated nut takes placecontinuously during travel of the nut N to the segment of the pathcorresponding to the blocked section 29(a). At this position, theturning member operates to turn the nut about the axes of its threadedsection and return it to the notch 24 in turned position with a new areaof the threaded surface available for deposition of powder during theportion of the path of travel onwardly of the blocked section 29(a).

Deposition of resin particles in two portions with the deposition areain fixed relation to the resin supply conduits during deposition of eachportion appears to be important for the development of a desirablelocking body. That is, on each of the areas on which the resin isdeposited, the first applied resin particles soften and adhere to thehot threaded surfaces and this softened resin is particularly effectivefor catching later applied particles progressively to build up thedeposit of resin in the desired thickness and contour and to transfersoftening heat from the hot threaded surface to melt the later appliedparticles so that the applied particles coalesce to a continuous body.

The thickness and to some extent the lateral dimensions of the resindeposits on the areas may be controlled by the temperatures of the nuts,the rate of supply of the resin particles and air, and the length oftime during which resin particles are applied to the areas, i.e. thetime required for a nut to be conveyed along one of the portions of thetreatment path. The resin deposits are thicker at their centers andtaper uniformly towards their edges. If desired, the deposits may becontrolled such that the edges of the deposits overlap to an extent thatthe combined thickness of the overlapping edge portions approximate thethickness of the centers to form in effect a unitary patch over thecombined area of the deposits to give a maximum locking effect for thelocking patch area. The deposition may of course, be controlled toprovide substantiallyseparate locking patches or any condition betweenseparate patches and a unitary patch.

In the embodiment shown, the table 10 is provided with about 60 tubes23, each tube projecting slightly into the nut N at approximately 45°.The powder is thus guided through the tube 23 to strike the internalthreads of the fastener at a point slightly above the lowermost threadand the air powder flow is adjusted such that very little powderimpinges upon the uppermost thread. As the tube 23 and the associatednut N rotate together over the 180° segment, a steady, rather uniformflow of powder is projected into the nut except at the intermediateportion where the nut is turned and flow of powder is cut off by theblocked section 29(a). Simultaneously, the vacuum hood 13 is drawingexcess material into the hood and away from the nut N during the 180°segment. The flow of "vacuum air" through the internal opening in thenut, and across the top of the nut, prevents powder from adhering to thenut except where powder impinges directly from the tube 23 onto the nutthreads.

After the tube 23 and associated nut N pass from the stage of operationwhere the aperture 22 is in registration with the slotted opening 29(and consequently from beneath the hood 13), there is a small arc ofabout 15° wherein the aperture 22 faces the outer periphery of thehousing 11, and therefore the tube 23 is substantially shut off. Atabout this point in the table movement, the nut confronts the leadingedge of the chute 14 and while still engaged in the V-shaped slot 24registers with the rail 51 of the chute. The nuts N are then forced intoflat-to-flat engagement by continuous movement of the table 10 and aremoved in a continuous stream between the inner rail 52 and outer rail 51of the chute 14, to be removed from the table 10 to a receiving point.

During the next approximately 150° arc of rotational path, a next stageof operation takes place wherein each of the tubes 23 has its aperture22 brought into registration with the slotted opening 34 which isconnected to the chamber 33 to which a vacuum is being applied. Thus,through an arcuate distance of 150°, each of the tubes 23 has a vacuumdrawn on it which evacuates any excess material from the tube 23 and theaperture 22.

As may be envisioned, in providing a tube 23 which is bent upwardly at a45° angle to distribute the powdered material in the described manner onthe internal threads of the nut N, particles of material may becomeimpinged on the outermost surface of the tube orifice and thereforewould be deposited on a subsequent nut as the nut in the heatedcondition was placed on the table and moved across the discharge orificeof the tube. By providing the vacuum chamber 33 and drawing the materialinwardly away from the orifice of the tube 23 the material issubstantially eliminated at the orifice, and the probability ofdepositing material at an undesirable location on a subsequent fasteneris thereby substantially eliminated.

The following Example is given as a possible aid in understanding theinvention more fully; but it is to be understood that the presentinvention is not limited to the particular materials, conditions, orprocedures of the Example.

EXAMPLE

A continuous succession of 3/8 inch - 16 hex nuts was supplied inflat-to-flat relation to the loading chute 12 of an apparatus as shownin the Figures with the table 10 rotating at about 4.3 revolutions perminute and a resin feed of about 23 grams per minute of a mixture ofpowdered polyamide resin (nylon 11) and a minor proportion of epoxyresin. The mixture had a particle size distribution such that less than2% was retained on a No. 70 Sieve, about 90% was retained on a No. 140Sieve and about 5% passed a No. 325 Sieve. In passing down the chute 12,the nuts were heated by the high frequency induction coil 50 to atemperature of about 575° F. and then moved into registry with theV-shaped notches 24 of the support table 10 with their lower facesresting on the tongues 25 of the table and with the lower openings ofthe nuts generally aligned with the openings in the tongues so that thedischarge ends of the particle directing conduits or tubes 23 extendwithin the open lower ends of the nuts for directing resin particlesagainst the threaded surfaces of the nuts. As the table rotated, air andentrained resin particles flowed from the slotted opening 29 through theconduits 23 and against the hot threaded surfaces to build up depositson first areas of the threaded surfaces of the nuts.

Approximately halfway along the arcuate path of the nuts from loadingchute 12 to unloading chute 14 the supply of resin powder to theconduits associated with the nuts reaching this location was blocked bythe segment 29(a) and the nuts were turned one flat by the turningdevice 62. After the nuts had been turned and moved past the turningdevice, supply of resin to the conduits 23 associated with the nuts wasresumed to build up a deposit on a further area of the threaded surface.Nuts carried to the unloading chute were lifted by the chute 14 awayfrom the support table 10 and pushed up the chute 14 by successive nutsreaching the chute.

After cooling, the nuts were tested for locking torque using Grade 5zinc phosphate and oil finished hex head screws. The nuts were seated to3,200 pounds before prevailing torque was measured.

Also for comparison, a succession of identical nuts was treated usingthe same conditions and the same machine except that the blockingsegment and turning device had been removed so that all resin wasdeposited in a single area.

The results of the torque tests of the nuts prepared using the processand apparatus of the present application with the nuts prepared withoutthe improvements of the present application are given in the followingtable:

    ______________________________________                                                           1st        5th                                                                removal    removal                                                   Installation                                                                           max/min    max/min                                         ______________________________________                                        Standard nuts*                                                                            69         36/25      28/17                                       Nuts rotated 60°*                                                                  61         50/37      39/27                                       Specification                                                                             80 max     12/5       8.5/4                                       ______________________________________                                         *Values average of 5 tests in lbs.-inch.                                 

Having thus described our invention what we claim as new and desire tosecure by Letters Patent of the United States is:
 1. Process forapplying locking patches of resilient resin to internally threadedarticles having openings at both ends of the threaded portionscomprising:conveying said articles in a path for treatment with the axesof their threaded portions in an up and down position and with theopenings at the upper and lower ends of the threaded portionssubstantially uncovered, heating said threaded portions of said articlesto a temperature above the softening point of resin to be applied,directing particles of heat fusible resin upwardly through said openingsat the lower ends of said articles against a first area of each of saidthreaded portions during movement in a first portion of said path tocause said resin particles to be softened by heat from said threadedportions and to build up a deposit on said area, sequentially turningeach of said articles about the axis of its threaded portion through apredetermined angle, less than 360°, at an intermediate location alongsaid path to dispose a further area of said threaded portion to receiveparticles, directing particles of heat fusible resin against saidfurther area of each of said threaded portions to build up a deposit onsaid further area during movement along the remaining portion of saidpath, coalescing the deposited resin particles, and cooling the resinfrom fused state to a solid resilient condition effective to providelocking action.
 2. Process as defined in claim 1 in which said depositsin said first areas and said further areas are thicker in centralportions than in edge portions.
 3. Process as defined in claim 2 inwhich said turning displaces said first area by an amount such that edgeportions of the resin deposited on said first area are overlapped byedge portions of resin deposited on said further areas to an extent thatthe thickness of the resin in overlapped portions approximates thethickness of the resin deposited in central portions of said first areaand said further area.